NEUTRINO MASS LIMITS FROM A PRECISE DETERMINATION OF BETA-BETA-DECAY RATES OF TE-128 AND TE-130

Double beta decay of Te-128 has been confirmed and the ratio of half-lives for betabeta decay of Te-130 and Te-128 has been determined as Te-130(1/2)/Te-128(1/2) = (3.52 +/- 0.11) X 10(-4) by ion-counting mass spectrometry of Xe in ancient Te ores. The Xe measurements, combined with common Pb dating, yield a Te-130 half-life of (2.7 +/- 0.1) x 10(21) yr and thus a Te-128 half-life of (7.7 +/- 0.4) x 10(24) yr. These results give limits on the effective Majorana mass of the neutrino (< 1.1-1.5 eV) and right-handed currents (\[eta]\ < 5.3 x 10(-8) comparable to the best obtained from direct neutrinoless betabeta-decay searches. They also imply new limits on nonstandard Majorons not constrained by measurements of the Z0 decay width.